Relaying should not have to be turned on for internal users. Outlook/MAPI does not relay mail and those settings do not apply to it. I do agree though that we need to know which server is issuing the NDR.

when u configure smtp mail connector there is two options which u can select one is use dns the other is a smart host.
if u use dns your system must be able to resolve domain name to ip by some how i mean u can run your own dns or use forwarders to query external dns servers.
but if u do not have or cannot use dns to resolve domain names then u can use smart host which can be another smtp server (commanly at your ISP) and it would accept messages from your server and route them to the intended recepients by using his own dns mechanism. if u specify a smart host u would be worry free for domain name resolution.

the messages shows that the communication blocked or rejected from the ip 193.248.49.145 by rbl-plus.mail-abuse.org. if this is yours fix ip then u should go to http://www.mail-abuse.org/ and check why they are blocking, if this is for your isp then ask them to solve this issue.

Unified and professional email signatures help maintain a consistent company brand image to the outside world. This article shows how to create an email signature in Exchange Server 2010 using a transport rule and how to overcome native limitations …

There are times when we need to generate a report on the inbox rules, where users have set up forwarding externally in their mailbox. In this article, I will be sharing a script I wrote to generate the report in CSV format.

In this video we show how to create a mailbox database in Exchange 2013. We show this process by using the Exchange Admin Center.
Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center.
Navigate to the Servers >> Data…